1. Field of the Invention
The present invention relates to a method of manufacturing a door glass run to be attached to a door frame of a motor vehicle and, more particularly, to a method of manufacturing a corner part in such a door glass run.
2. Description of Related Art
As illustrated in FIG. 1, a door glass run (hereinafter will be merely called glass run) R is attached along an inner periphery of a door frame 12 of a door 10 of a motor vehicle to guide a door glass 14 to its closed and open positions, and effect a seal between the door glass 14 and door frame 12 when the door glass 14 is fully closed. The glass run has a generally U-shaped cross-section and is formed linearly by extruding solid rubber.
The glass run thus extruded, however, cannot be bent in conformity with a corner of the door frame 12, which curves at right angles, such as a corner C1 in FIG. 1. So, generally, two extruded glass runs have been joined together with a corner member which is molded so as to curve at right angles.
Corner parts of the glass run to be attached to gently curved corners of the door frame 12 such as corners C2 and C3 in FIG. 1 can be obtained by forming a cutout in a bottom wall of an extruded glass run over a length corresponding to the corner of the door frame 12, bending the glass run to a desired corner configuration, placing the bent corner part of the glass run in a mold, and injecting a rubber material into the mold to fill the cutout with the rubber material.
With this method, however, upon bending the glass run having such a cutout, the cross-sectional configuration of the glass run may be irregularly deformed, which makes it difficult to place the glass run in the mold. In addition, upon closing the mold, the glass run thus irregularly deformed may be partly caught between mold members.
To prevent irregular deformation, conventionally, a plurality of lateral slits have been formed separately in a bottom wall of an extruded glass run, and the glass run having the lateral slits has been bent into a desired corner configuration, which results in, as shown in FIG. 2, the slits being opened to define a plurality of notches 16, each having a V-shaped cross-section. Then, the notches 16 have been filled with molding material 18 in a mold (Japanese Patent application-laid open No. Hei 6-134855).
This method for forming a corner part in the glass run may be applied to a corner of the door frame, which curves at right ingles, such as the corner C1 in FIG. 1.
However, when the above method is applied to the door glass run R1 shown in FIG. 3, which has the arrangement that one side wall 20 to be located inwardly upon installed on the door frame 12 has a height greater than that of the other side wall 22 to be located outwardly upon installed on the door frame 12, there occurs the following problem. After removing the molded corner part from the mold, as shown in FIG. 3, the side wall 20 having a volume greater than that of the side wall 22, protrudes upwardly to abut the door frame 12, thus generating a buckle 26 in the side wall 22. This is caused by the difference in residual stress between the side walls 20 and 22 which have been bent and placed in the mold.
Due to these deformations, the molded corner of the glass run R1 cannot be installed on the door frame 12 in a normal state, whereby the sealing performance around the door glass is lowered.